U.S. Pat. No. 4,136,306 to Westlund et al, entitled, "Apparatus for Preparing Pattern Control Data" discloses an optical viewing system which is utilized for entering pattern data into an automatic sewing machine. The optical viewing system illuminates a portion of a movable X-Y table which allows the operator of the sewing machine to view a model of the desired pattern located on the table. The model of the desired pattern is projected onto a viewing screen having cross hairs thereon. The pattern model is caused to move while under the manual control of the operator. In this regard, the operator positions various points of the pattern relative to the cross hairs so as to define coordinates of the stitch pattern. These coordinates are digitized and thereafter recorded into the memory of a computer associated with the automatic sewing machine.
It is to be appreciated that the illumination provided in the optical viewing system of U.S. Pat. No. 4,136,306 is only for the purpose of illuminating an area that is to be projected onto the viewing screen. The illumination is not itself used as a reference for positioning various points of the pattern.
The image projection system of U.S. Pat. No. 4,136,306 also requires an appreciable offset relative to the sewing needle. This offset is due to the considerable structure associated with the viewing system. The offset dictates how far the positioning system must be extended to the one side of the sewing machine so as to allow for a complete digitizing of a pattern. Typical positioning systems for an automatic sewing machine do not allow for such an appreciable displacement to the one side of the sewing machine. This had led to the mounting of auxiliary holding devices associated with the positioning system so as to thus hold the pattern that is to be digitized to the one side of the sewing machine. This auxiliary holding device has introduced objectionable inaccuracies into the positioning of the thus mounted pattern. This has furthermore added an appreciable amount of time to the digitizing process.